Kyodo

Kyodo is the art of being guided by locals. A shinobi would obtain vital information about the landscape simply by asking a local about it. Sometimes, out of the need for secrecy, the local would be killed.

According the Sun Tzu's Art of War:

Without knowing the lie of hills and woods, of cliffs and crags, of marches and fens, you cannot march. Without using local guides, you cannot exploit the lie of the land. Ignorance of any one of these points is not characteristic of the army of a great king.